| In recent years, a new deforming eutectic Al-Si alloy, which can be reinforced by heat treatment, has been developed by the way of semi continuous casting. Not only has it high strength, tow thermal expansion coefficient, but also it has the advantages of good corrosion resistance, wear resistance and weld ability, thus it is widely used in the industry. Silicon particle shape and size of the alloy are improved by semi continuous casting, heat treatment and plastic working, thus the alloy acquires good plasticity, turning casting alloy into deforming alloy. But the study on the structure and properties of high silicon wrought aluminum alloy with magnesium content is not comprehensive. Especially the effects on the structure and properties of the second relative of the high silicon wrought aluminum alloy are still in its infancy. According to the new high silicon wrought aluminum alloy with magnesium, we studied how to control the silicon particle size and its coarsening behavior. Then, we studied the effect of mechanical properties when the silicon particle size and distribution are different. At the same time, we discussed the effects of precipitation state of Mg2Sion mechanical properties and strain-hardening indices. Finally, we observed the effects of silicon particle on crack propagation behavior when the precipitation state of Mg2Si is different. The results are shown below:1. Semi-continuous Al-12.7St-0.7Mg alloy ingot when heating on 425?x1.5h and after 83% deformation with hot rolled plate, the eutectic silicon have break to particles. Then, after solutioned on 530?×15min, silicon particle become spheroidization. When the deformation is between 83% and 92%, the size, morphology and distribution of silicon particle has no obvious change on solution treatment.2. Semi-continuous Al-12.7Si-0.7Mg alloy ingot when heating on 425?×1.5h and after 83% deformation with hot rolled plate, when processing between 410? and 540?, the eutectic silicon particles significantly larger flow was significantly increased. Silicon particles mean radius increases rapidly in early time, but the increasing rate would be lower when time is longer.3. The hot rolled plate of Al-12.7Si-0.7Mg alloy casting by semi-continuous, the r3-t curve of eutectic silicon particle is in the form of a parabolic at the early stage of the coarsening. The r3-t relationship of eutectic silicon particle is approximate linear relationship after coarsening in the certain degree, kinetic constant of particle coarsening is gradually increasing as the temperature rises, so its Ostwald coarsening behavior conform to the classical theory of LSW. At the later stage of the coarsening, kinetic constant of particle coarsening would be guadually decreasing, the r3-t relationship of eutectic silicon particle is not a straight line.4. The hot rolled plate of Al-12.7Si-0.7Mg alloy casting by semi-continuous, when the precipitation state of Mg2Si is constant, alloy yield strength changed little as the eutectic silicon particle size increases and distribution is thinning, and when the silicon particle size is between 0.50?m and 0.58?m, tensile strength is basically the same, but when the silicon particle size is between 0.58?mand 3.53?m, tensile strength is declining.5. The hot rolled plate of Al-12.7Si-0.7Mg alloy casting by semi-continuous, When the silicon particle size is about 0.73?m, and alloy matrix is peak aging state, water quenching state and annealing state, Rp0.2?Rm?A of the rolled plate is respectively 288.4 MPa,354.6 MPa,11.3%,115.8 MPa,268.3 MPa,18.6% and 56 MPa,139 MPa,28.7%. It is shown that mechanical properties of this alloy are depending on its matrix state. With the increase of matrix hardness of the alloy plate, crack tip propagation is by passing the silicon particle to cutting the silicon particle.6. The hot rolled plate of Al-12.7Si-0.7Mg alloy casting by semi-continuous, the arrange of total strain strengthening index from big to small is water quenching state, natural aging twelve days state, annealing state and peak aging state. But according to the plate of artificial aging state, with the extension of aning time, the strain strengthening index decreases first and then increases.7. With the increase of end point of strain, the continuous strain strengthening index of annealing samples increase first and then become stable, the continuous strain strengthening index of warter quenching samples decrease first and then increase and then become stable, and the continuous strain strengthening index of aging samples decrease first and then become stable. With the increase of stage strain, the stage strain strengthening index of annealing samples increase first and then become decrease, the stage strain strengthening index of warter quenching samples and natural aging samples gradually increase, and the stage strain strengthening index of artificial aging samples decrease sharply first and then increase slowly?... |
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